A route-planning app measures the drive from New York to Los Angeles in meters: about 4 490 000 m. The number is correct, and useless to say out loud.
You've already seen the SI base units: the meter, the second, and the kilogram. Written straight in a base unit, some measurements come out as clunky numbers.
Put kilo- on the front of the meter, and the same drive reads 4 490 km. That is a number you can say out loud. kilo- means one thousand: 1 km is 1000 m.
A word part attached to the front of a unit, scaling it by a fixed amount, is called a metric prefix.
centi- means one hundredth: 1 cm is 0.01 m, about the width of a fingernail. milli- means one thousandth: 1 mm is 0.001 m, and an ant is about 4 mm long.
What does the prefix milli- mean?
A prefix can attach to the front of any unit. A millisecond is one thousandth of a second.
Mass is the odd one out: its SI base unit, the kilogram, already carries a prefix. kilo- attached to the gram: 1 kg is 1000 g.
How many grams are in 1 kilogram? Enter the number.
Which statement is correct?
How many millimeters together make 1 meter? Enter the number.
Four lengths are listed: 1 km, 1 m, 1 cm, 1 mm. Which is the longest?
A motion sensor logs a reading every 1 centisecond. How much time passes between readings?